Actuator and liquid discharge head, and method for manufacturing liquid discharge head

ABSTRACT

An actuator comprises a laminated structure having a vibration plate, a lower electrode, a piezoelectric element, and an upper electrode laminated sequentially on a basic element, and then, at least the lower electrode of the two electrodes is a thin oxide film doped with La of single orientated crystal or monocrystal that contains Sr and Ti. Thus, it is made possible to materialize the micro miniaturized actuator having a strong structure of lamination with high adhesion, which is capable of obtaining large displacement with sufficient durability without spoiling the piezo-electrostrictive property thereof even with the small thickness of the piezoelectric element. With the micro miniaturized actuator thus structured, it is made possible to make a liquid discharge head more precisely.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to an actuator used for a liquiddischarge head mounted on a liquid discharge recording apparatus, aswell as to a liquid discharge head. The invention also relates to amethod for manufacturing a liquid discharge head.

[0003] 2. Related Background Art

[0004] In recent years, the printer that adopts a liquid dischargerecording apparatus as the printing apparatus for a personal computerand the like has been widely used for the reasons that it has anexcellent printing performance with easier handling at lower costs,among some others. For the liquid discharge recording apparatuses of thekind, there are those adopting various methods; the one that dischargesliquid droplets by means of the pressure wave of the bubble, which isgenerated by bubbling in liquid, such as ink, by the application ofthermal energy; the one that enables liquid droplets to be sucked anddischarged by means of electrostatic force; and the one that utilizesthe pressure wave generated by a vibrator, such as piezoelectricelement, and some others. Generally, the one that uses piezoelectricelement is structured with a pressure chamber communicated with a liquidsupply chamber, and a liquid discharge port communicated with thepressure chamber, for example, and there is provided a vibration platehaving piezoelectric element connected with the pressure chamber. Then,with the structure thus formed, the piezoelectric element is stretchedand constricted by the application of a specific voltage to thepiezoelectric element so as to generate straining vibrations forcompressing liquid, such as ink, in the pressure chamber, thusdischarging liquid droplets form the liquid discharge ports.

[0005] In recent years, color liquid discharge apparatuses have been inwide use, and along with this, it has been required to enhance theprinting performance, such as higher resolution, and higher printingspeed, in particular. Further, it is required to implement theelongation of liquid discharge head, necessitating the materializationof a multiple-nozzle head structure, which is a more preciselystructured liquid discharge head. Then, there is a need forminiaturizing an actuator for discharging liquid in order to make theliquid discharge head more precisely. For the miniaturization ofpiezoelectric element and/or electrostrictive element (hereinafterreferred to as a piezo-electrostrictive element), which constitutes theactuator of the liquid discharge head, it is necessary for thepiezoelectric element itself to be made smaller, and then, to beprovided with a high piezoelectric constant so as not to allow thedriving performance thereof to be lowered even if the element is madesmaller.

[0006] It is then necessary for the piezoelectric and/orelectrostrictive film (hereinafter referred to as anpiezo-electrostrictive film) whereby to form the piezoelectric elementto be a film having an excellent crystallinity. The film that has theexcellent crystallinity is a thin film of the single-orientated crystal,which is orientated in one and the same direction or the monocrystalhaving in-plane orientation. Also, to make the piezo-electrostrictivefilm of monocrystal, it is desirable that the immediate layer ismonocrystal or the like when manufacturing the piezo-electrostrictivefilm, and the combination of the piezo-electrostrictive film and thematerial of the immediate layer should be given an excellent latticematching.

[0007] However, for the piezo-electrostrictive film used for theconventional piezo-electrostrictive element, it is difficult to form thepiezo-electrostrictive film thinner than 10 μm, for example, because theadopted method of the film formation is such that the powered paste ofPbO, ZrO₂, and TiO₂ is processed to be a sheet (green sheet) by molding,and after that, the sheet is sintered for the film formation. Also, thesintering of the green sheet is performed at a temperature of 1,000° C.or more. As a result, a problem is encountered that thepiezo-electrostrictive material is contracted almost to 70% unavoidably.Under such circumstances, it is difficult to position thepiezo-electrostrictive element and the structures, such as the liquidchamber and the pressure chamber, together in a high precision ofseveral-micron order. It is, therefore, difficult to miniaturize theactuator.

[0008] Also, the ceramics piezo-electrostrictive film, which is formedby sintering the green sheet, the influence of the grain boundarybecomes no longer negligible as the thickness thereof is made smaller.It is then difficult to obtain any good piezo-electrostrictive property.In other words, for the piezo-electrostrictive film obtained bysintering the green sheet, there is a problem that it is difficult toobtain any sufficient piezo-electrostrictive property for dischargingrecording liquid if the thickness thereof becomes less than 10 μm. Underthe circumstances, it has been difficult to materialize a small liquiddischarge head having the characteristics needed for dischargingrecording liquid sufficiently.

[0009] Also, as the method of manufacture of the piezo-electrostrictivefilm, which has been reported up to the present, there are CVD method,Sol-Gel method, and others. The density of piezo-electrostrictive filmmanufactured by these methods also tends to be lowered to make the microprocessing thereof difficult. The piezoelectric constant that indicatesthe capability of the piezo-electrostrictive material is small, too.Therefore, the displacement amount becomes small against a constantvoltage accordingly when it is miniaturized. Thus, it is difficult toadopt the aforesaid CVD method and the like for manufacturing a smallactuator and the piezo-electrostrictive film for a liquid dischargehead.

[0010] Further, with respect to the conventional art, a problem isencountered that the adherence is made lower between metallic electrodesand the piezo-electrostrictive element, which is oxide. There is a needfor the provision of high adherence between the electrodes andpiezo-electrostrictive film in order to withstand the stress that occursby the repeated driving when acting as an actuator andpiezo-electrostrictive element for a liquid discharge head.

[0011] Also, the structure of a liquid discharge head manufactured bythe micro processing of semiconductor process using sputtering method,and the method of manufacture therefor have been proposed in thespecification of Japanese Patent Application Laid-Open No. 11-348285.This liquid discharge head is characterized in that on the mono-crystalMgO, platinum is orientated for the film formation, and further,thereon, the perovskite layer that does not contain Zr layer, and thePZT layer are formed as a laminated element.

[0012] However, with the method of manufacture disclosed in thespecification of the aforesaid laid-open paten application, it isdifficult to obtain the single-orientated crystal, which is stabilizedwith good reproducibility or monocrystal PZT. Further, it is impossibleto obtain the PZT layer unless it is orientated on an extremelyexpensive monocrystal substrate, such as monocrystal MgO. The processbecomes extremely expensive unavoidably. Further, there is a limit tothe size of the MgO mono-crystal substrate to make it difficult toobtain the substrate having a large area.

[0013] In this respect, as the oxide electrode material, there is adisclosure of the element that uses SrRuO₃ in the specification ofJapanese Patent Application Laid-Open No. 06-280023. However, in thisspecification of patent application, there is no disclosure that SrRuO₃is a crystal having single-orientation or monocrystal, and the thinoxide piezo-electrostrictive film, which should be formed on the upperpart, cannot become a crystal having single-orientation or amonocrystal.

SUMMARY OF THE INVENTION

[0014] One of the object of the present invention is to provide anactuator capable of materializing a stable and highly reliable liquiddischarge head having liquid discharge ports formed in high density bythe use of a high-strength laminated structure containing a thinnerpiezo-electrostrictive film having sufficient piezo-electrostrictiveproperty, which makes it possible to perform the micro processinggenerally used for the semiconductor process, as well as to provide suchliquid discharge head, and a method for manufacturing the liquiddischarge head.

[0015] It is another object of the invention to provide a method formanufacturing a liquid discharge head capable of forming apiezo-electrostrictive film of single orientated crystal or monocrystalstably with good reproducibility.

[0016] It is still another object of the invention to provide anactuator having a piezo-electrostrictive element with large displacementamount and high adhesion between a piezo-electrostrictive film andelectrodes, and also, to provide a liquid discharge head, and a methodfor manufacturing the liquid discharge head.

[0017] It is a further object of the invention to provide an actuatorcomprising a laminated structure having a vibration plate, a lowerelectrode, a piezoelectric element, and an upper electrode laminatedsequentially on a basic element, in which at least the lower electrodeof the two electrodes is a thin oxide film of La doped single orientatedcrystal or monocrystal containing Sr and Ti.

[0018] It is still a further object of the invention to provide a liquiddischarge head having the main body portion with pressure chambercommunicated with liquid discharge port, and an actuator provided on themain body portion corresponding to the pressure chamber, in which theactuator comprises a laminated structure having a vibration plate, alower electrode, a piezoelectric element, and an upper electrodelaminated sequentially on a basic element, and then, at least the lowerelectrode of the two electrodes is a thin oxide film of La doped singleorientated crystal or monocrystal containing Sr and Ti.

[0019] It is still another object of the invention to provide a methodfor manufacturing a liquid discharge head provided with the main bodyportion having pressure chamber communicated with liquid discharge port,and an actuator provided on the main body portion corresponding to thepressure chamber, comprising the steps of filming a vibration plate onthe main body portion; filming on the vibration plate a lower electrodeof thin oxide film of La doped single orientated crystal or monocrystalcontaining La doped Sr and Ti; filming on the lower electrode aperovskite type thin oxide piezo-electrostrictive film; filming an upperelectrode on the perovskite type thin oxide piezo-electrostrictive film;and forming the pressure chamber.

[0020] When the piezoelectric element of the actuator is formed by theoxide piezo-electrostrictive film of single orientated crystal ormonocrystal, which is thin but provides excellent piezo-electrostrictiveproperty, it becomes possible to perform micro processing by use of thesemiconductor process. For the manufacture of such thin oxidepiezo-electrostrictive film of single orientated crystal or monocrystalstably and in good reproducibility, a thin oxide film of La doped singleorientated crystal or monocrystal, which contains Sr and Ti, is used toform the lower electrode that becomes the layer thereof when beingfilmed. The electrode of thin oxide film doped with La of singleorientated crystal or monocrystal containing Sr and Ti has good latticecontrollability with the oxide piezo-electrostrictive material thatforms the piezoelectric element. Therefore, it is made possible to formon the lower electrode the piezo-electrostrictive film of singleorientated crystal or monocrystal having the crystal orientation ratioof 90% or more.

[0021] Also, when both of two electrodes bonded to the piezoelectricelement are those of the thin oxide film having high crystallinity asdescribed above, the strength of the two electrodes, upper and lower,themselves are made high, and also, the adhesion thereof becomesexcellent with respect to the piezoelectric element, which significantlycontributes to the reinforcement of strength and the enhancement ofdurability of the laminated structure that forms the actuator.

[0022] Then, when the piezoelectric element having sufficientpiezo-electrostrictive property is formed to be a highly stronglaminated structure, which is filmed in a small thickness of 10 μm orless, for example, the micro processing using the semiconductor processbecomes applicable to the manufacture of the actuator, hence making itpossible to promote the miniaturization of the actuator, and theprovision of a liquid discharge head in high density, as well as thehigher performance thereof.

[0023] For the present invention, the thin oxide film doped with La ofsingle orientated crystal or monocrystal containing Sr and Ti is used asthe lower electrode. As a result, it becomes possible to epitaxiallydevelop on the lower electrode the piezo-electrostrictive film ofperovskite type or the like stably and in good reproducibility. With thelamination of such piezoelectric element and electrodes of thin oxidefilm of single orientated crystal or monocrystal, it becomes possible tomaterialize the micro miniaturized actuator having a strong structure oflamination with high adhesion, which is capable of obtaining largedisplacement with sufficient durability without spoiling thepiezo-electrostrictive property even with the small thickness of thepiezoelectric element. By use of such actuator it is possible tomaterialize a high-performance liquid discharge head in extremely highdensity.

BRIEF DESCRIPTION OF THE DRAWINGS

[0024]FIG. 1 is a perspective view that schematically shows a liquiddischarge head in accordance with one embodiment of the presentinvention.

[0025]FIG. 2 is a perspective view that schematically shows an actuatorused for the liquid discharge head represented in FIG. 1.

[0026]FIG. 3 is a partially broken perspective view that shows thesectional structure of the liquid discharge head represented in FIG. 1.

[0027]FIG. 4 is a view that shows the manufacturing process of theliquid discharge head in accordance with one embodiment of the presentinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0028] Hereinafter, with reference to the accompanying drawings, thedescription will be made of one embodiment in accordance with thepresent invention.

[0029]FIGS. 1, 2 and 3 illustrate a liquid discharge head embodying thepresent invention. The liquid discharge head M comprises the main bodybase plate portion 1, which serves as the basic element; pluraldischarge ports (nozzles) 2; plural pressure chambers (liquid chambers)3 provided for each of the liquid discharge ports 2; and the actuator10, which is arranged corresponding to each of the pressure chambers 3,respectively. The liquid discharge ports 2 are formed for a nozzle plate4 at predetermined intervals. The pressure chambers 3 are formed inparallel on the main body basic plate portion 1 corresponding to theliquid discharge ports 2, respectively. Here, for the presentembodiment, the liquid discharge ports 2 are arranged on the lower faceside. However, these ports may be arranged on the side face side.

[0030] On the upper face of the main body base plate portion 1, eachopening (not shown) is formed for each of the pressure chambers 3correspondingly, and each of the actuators 10 is positioned to closesuch opening. Each of the actuators 10 comprises a vibration plate 11formed by thin oxide film; a piezoelectric element(piezo-electrostrictive film) 12; and the lower electrode 13 and upperelectrode 14, which are formed by thin oxide film, respectively.

[0031] Of the aforesaid two electrodes 13 and 14, at least the lowerelectrode 13, which lies between the vibration plate 11, and thepiezoelectric element 12, which is the thin oxide piezo-electrostrictivefilm, is the electrode formed by thin oxide film of single-orientatedcrystal or monocrystal that contains La doped Sr and Ti and presentsgood lattice controllability with respect to both the thin oxide film ofthe vibration plate 11 and the thin oxide piezo-electrostrictive film.

[0032] For the present embodiment, the thin oxide film electrode is usedat least for the lower electrode. Therefore, the strength of theelectrode itself, and the adhesion with the vibration plate formed bythin oxide film can be kept even if the mechanical displacements arerepeated and minute cracks are generated. Also, with the selectedelectrode material, which presents good matching of lattice constantboth with the vibration plate and the thin oxide piezo-electrostrictivefilm, the adhesive force is not deteriorated, hence making it possibleto materialize the microminiaturized piezo-electrostrictive element(actuator) having excellent durability.

[0033] In addition, on the lower layer of the thin oxidepiezo-electrostrictive film that forms the piezoelectric element, theelectrode, which is a single-oriented crystal or monocrystal with goodlattice matching with the thin oxide piezo-electrostrictive film, isarranged to exist inclusively. Then, it is made possible to obtain thesingle-orientated crystal or monocrystal piezo-electrostrictive filmwith high ratio of crystal orientation stably and in goodreproducibility.

[0034] Further, the vibration plate and piezoelectric element, and bothelectrodes, which are laminated on the basic element, are formed oneafter another by the film having uniform crystal orientation. In thisway, it is made possible to minimize the variations in the actuatorperformance per nozzle in the case of a liquid discharge head, and also,to obtain a device having a strong adhesion.

[0035] As described above, in the laminated structure of a singleorientated crystal or monocrystal containing an upper electrode, apiezoelectric element, a lower electrode, and a vibration plate, inwhich at least the lower electrode of the aforesaid two electrodescontains a chemical element containing La doped Sr and Ti, it ispreferable to keep the concentration of the La, which is doped in theaforesaid electrode of thin oxide film, within a range of 0.05 atm % to10 atm %.

[0036] The crystallinity of the electrode of thin oxide film the Laconcentration of which is 0.05 atm % to 10 atm % tends to bedeteriorated as the La concentration increases. However, with theincreased La concentration, the conductance can be made larger from1×10³ (S/cm) to 1×10⁵ (S/cm). Therefore, it is preferable to keep the Laconcentration doping within a range of 0.05 atm % to 10 atm %.

[0037] Also, it is preferable to keep the lattice constant of the Ladoped electrode of thin oxide film within a range of 3.905 Å to 4.030 Å.As the La concentration is increased from 0.05% to 10%, the latticeconstant of the electrode of thin oxide film becomes larger from 3.905 Åto 4.030 Å, and the lattice constant of the electrode of thin oxide filmcan be made to match with a desired lattice constant, which is closestto the lattice constant of the piezo-electrostrictive film to be formedthereon.

[0038] Also, it is preferable to keep the film thickness of theaforesaid electrode of thin oxide film within a range of 50 nm to 5,000nm. It is more preferable to keep it within a range of 100 nm to 2,000nm. If the film thickness of the electrode of thin oxide film is lessthan 50 nm, it is impossible to secure sufficient conductance for thelower electrode. Also, if it is more than 5,000 nm, the surfaceroughness of the electrode of thin oxide film is large, which requiresthe mechanical polishing process. Then, there is a possibility that thecrystallinity and the conductance of the electrode of thin oxide filmare deteriorated.

[0039] Also, preferably, the crystal orientations of the substratesurface of the aforesaid electrode of thin oxide film are (010), (101),(110), and (111). Then, When the crystal orientations of the substratesurface of the electrode of thin oxide film serving as the lowerelectrode are (010), (101), (110), and (111), the piezo-electrostrictivefilm, which is formed on the upper part, is epitaxially developed tomake the crystal orientations of the piezo-electrostrictive film (100),(001), (010), (101), (110), and (111), respectively. In this respect,the piezo-electrostrictive property of the piezo-electrostrictive filmis particularly excellent when the crystal orientations are (001) and(111).

[0040] Also, preferably, the crystal orientation ratio of the aforesaidelectrode of thin oxide film is 90% or more. The crystal orientationratio means a ratio at the peak strength ratio of the film obtainable bymeans of the θ-2θ measurement of XRD (X ray analysis). When the crystalorientation ration of the electrode of thin oxide film is less than 90%,not only the good electrical property is impeded, but also, there is apossibility that the crystallinity of the piezo-electrostrictive filmformed on the upper part is deteriorated, because there exists thecrystal, which is provided with other orientations of more than 10%, ordifferent phase. More preferably, therefore, the crystal orientationratio should be 95% or more for the electrode of thin oxide film, whichserves as the lower part electrode.

[0041] The piezo-electrostrictive film that forms the piezoelectricelement should desirably be the thin oxide film of single-orientatedcrystal or monocrystal, which contains Pb, and at least one kind of atomfrom among Zr, Ti, Ni, Nb, Mg, Zn, and Sc.

[0042] As the material of the thin oxide piezo-electrostrictive film(piezo-electrostrictive film) of single-orientated crystal ormonocrystal, which is used for the present invention, the following canbe selected, for example:

[0043] PZT [Pb(Zr_(x)Ti_(1−x))O₃],

[0044] PMN [Pb(Mg_(x)Nb_(1−x))O₃],

[0045] PNN [Pb(Nb_(x)Ni_(1−x))O₃],

[0046] PSN [Pb(Sc_(x)Nb_(1−x))O₃],

[0047] PZN [Pb(Zn_(x)Nb_(1−x))O₃],

[0048] PMN-PT {(1−y)[Pb(Mg_(x)Nb_(1−x))O₃]-y[PbTiO₃]},

[0049] PSN-PT {(1−y)[Pb(Sc_(x)Nb_(1−x))O₃]-y[PbTiO₃]},

[0050] PZN-PT {(1−y)[Pb(Zn_(x)Nb_(1−x))O₃]-y[PbTiO₃]}

[0051] Here, the x and y are numbers less than 1 and more than 0. Forexample, in the case of PZT, preferably, the x is 0.3 to 0.7, that ofPMN, x is 0.2 to 0.5, and that of PSN, x is 0.4 to 0.7. Also,preferably, the y for PMN-PT is 0.2 to 0.4, the y for PSN-PT is 0.35 to0.5, and the y for PZN-PT is 0.03 to 0.35.

[0052] The thin oxide piezo-electrostrictive film of single orientatedcrystal or monocrystal may be a single composition or a combination oftwo or more kinds. Also, the film may be a composition formed by dopinga minute quantity of atom in the aforesaid main component.

[0053] Then, preferably, the crystal orientation ratio of the aforesaidpiezo-electrostrictive film is 90% or more. If the crystal orientationratio of the piezo-electrostrictive film is less than 90%, there existsthe crystal, which is provided with other orientations of more than 10%,or different phase, and it may cause the piezo-electrostrictive propertyof the actuator to be deteriorated.

[0054] Also, the crystalline system of the thin oxidepiezo-electrostrictive film of single orientated crystal or monocrystalshould preferably be rhombohedral or tetragonal. In other words, thereis a need for the piezo-electrostrictive film of single orientatedcrystal or monocrystal to be of the rhombohedral or tetragonal system toobtain the piezo-electrostrictive property good enough to provide thefunction to drive the actuator and liquid discharge head sufficiently.

[0055] The film thickness of the piezo-electrostrictive film of singleorientated crystal or monocrystal should preferably be 100 nm or moreand 10 μm or less. The material of the piezo-electrostrictive film ofsingle orientated crystal or monocrystal needs to be the one that canwithstand the stress generated by the repeated driving when it is usedfor the actuator and liquid discharge head. If the film thickness of thepiezo-electrostrictive film of single orientated crystal or monocrystalis leas than 100 nm, there is a possibility that it is broken due todefects when repeatedly driven. More preferably, the film thicknessthereof should be 500 nm or more and 8 μm or less.

[0056] Now, the specific layer structures of the actuator that uses theaforesaid electrode of thin oxide film of single orientated crystal ormonocrystal as the lower electrode in accordance with the presentinvention are listed below. The indication of the layer structure is:upper electrode //piezo-electrostrictive film//lower electrode/vibrationplate in that order.

[0057] Example 1 Pt/Ti//PZT(001)//La-STO(100)//YSZ(111)/Si(111)

[0058] Example 2 Au//PZT(001)//La-STO(100)//YSZ(111)/Si(111)

[0059] Example 3 La-STO(100)//PZT(001)//La-STO(100)//YSZ(111)/Si(111)

[0060] Example 4 Pt/Ti//PZT(001)//La-STO(100)/Si(111)

[0061] Example 5 Au//PZT(001)//La-STO(100)/Si(111)

[0062] Example 6 La-STO(100)//PZT(001)//La-STO(100)/Si(111)

[0063] Example 7 Pt/Ti//PZT(111)//La-STO(111)//YSZ(100)/Si(100)

[0064] Example 8 Au//PZT(111)//La-STO(111)//YSZ(100)/Si(100)

[0065] Example 9 La-STO(111)//PZT(111)//La-STO(111)//YSZ(100)/Si(100)

[0066] Example 10 Pt/Ti//PZT(111)//La-STO(111)//Si(100)

[0067] Example 11 Au//PZT(111)//La-STO(111)//Si(100)

[0068] Example 12 La-STO(111)//PZT(111)//La-STO(111)//Si(100)

[0069] For the specific examples listed above, the laminated layerstructure of PZT or PZT/PT is exemplified for the piezo-electrostrictivefilm. However, it may be the layer structure in which these areappropriately modified to the aforesaid PMN, PZN, PSN, PNN, PMN-PT,PSN-PT, or PZN-PT. For example:

[0070] Pt/Ti//PMN(001)/PT(001)//La-STO(100)//YSZ(100)/Si(100),

[0071] Au//PMN-PT(001)//La-STO(100)//YSZ(100)/Si(100),

[0072] La-STO(100)//PMN-PT(001)/PT(001)//La-STO(100)//YSZ(100)/Si(100)and others.

[0073] Here, the crystal orientations indicated in ( ) are those ofpreferred orientations described earlier.

[0074] The method for manufacturing the liquid discharge head describedabove comprises the steps of filming the vibration plate on the Sisubstrate that constitutes the main body basic element; filming theaforesaid electrode of thin oxide film on the vibration plate as thelower electrode; filming the piezo-electrostrictive film of perovskitetype on the electrode of thin oxide film; filming the upper electrode onthe piezo-electrostrictive film of perovskite type; forming the pressurechamber on the Si substrate; and bonding the nozzle plate havingdischarge ports formed therefor to the pressure chamber.

[0075] The filming process of the electrode of thin oxide film dopedwith La is to epitaxially develop the thin oxide film, which contains Srand Ti by use of sputtering method, MOCVD method, Sol-Gel method, MBEmethod, hydrothermal synthesis method, or the like.

[0076] The filing process of the piezo-electrostrictive film ofperovskite type on the electrode of thin oxide film is to epitaxiallydevelop the piezo-electrostrictive material of perovskite type by use ofsputtering method, MOCVD method, Sol-Gel method MBE method, hydrothermalsynthesis method, or the like.

[0077] The filming process of the upper electrode on thepiezo-electrostrictive film of perovskite type is to execute filming byuse of vapor method, such as sputtering method, vapor deposition methodor liquid method, such as plating method.

[0078] The forming process of the pressure chamber on the Si substrateis to form the pressure chamber on the Si substrate by use of the wetetching, which utilizes the anisotropic etching, or dry etching such asICP, legal process, Bosch process. Also, the shape of the pressurechamber can be selected from among rectangle, Circle, oblong, or thelike. Also, in a case of side shooter, the sectional shape of thepressure chamber may be such as to make it narrower in the nozzledirection.

[0079] The process of bonding the pressure chamber to the nozzle platehaving discharge ports formed therefor is to bond the nozzle platehaving nozzles provided therefor to each of the pressure chamber portioncorrespondingly. Also, the nozzle may be formed by resist material orthe like. Also, the nozzle may be formed by laser process correspondingto each pressure chamber after the polymer base plate has been bonded.

[0080] With the actuator of the present embodiment, it is possible tomaterialize a fine liquid discharge head having large discharging powerto deal with high frequency, because the piezo-electrostrictive filmthat forms the piezoelectric element is single orientated crystal ormonocrystal.

[0081] Next, the embodiments will be described.

First to Fourth Embodiments

[0082] For the actuator structured as shown in FIG. 2, the La dopingconcentration in the SrTiO₃ lower electrode is arranged to be 0.08%,0.80%, 8.00%, and 0.04%, and then, in accordance with the manufacturingsteps shown in FIG. 4, actuators of first, second, third, and fourthembodiment are manufactured.

[0083] The method of manufacture is as follows:

[0084] At first, a vibration plate is filmed on Si substrate bysputtering method (S1). At this juncture, the substrate is heated toform the film, while keeping the temperature at 500° C. or more. Thus,the vibration plate is epitaxially developed to make it monocrystal orsingle orientated one. Further, with the same method, the lowerelectrode is filmed on the vibration plate (S2) to make it possible toobtain the electrode of thin oxide film of monocrystal or singleorientated crystal. Then, with the same method, thepiezo-electrostrictive film is formed on the lower electrode (S3) tomake it possible to obtain the piezoelectric element (PZT) formed bythin film of monocrystal or single orientated crystal. The upperelectrode is also filmed in the same way (S4). Then, the rear andcentral parts of the Si substrate, which serves as the basic element,are removed by wet anisotropic etching (S5), thus manufacturing theactuator shown in FIG. 2.

[0085] Table 1 shows the relations of the lattice constant of La-STO andthe La doping concentration to the SrTiO₃ (STO) that forms the lowerelectrode; the relations with the orientation ratio of PZT, which is thepiezoelectric element; and PZT crystalline system. The structure andfilm thickness of each layer of the first, second, third, and fourthembodiments are as follows. In this respect, the indication in ( ) ispreferred direction of orientation, and the indication in [ ] is thefilm thickness, respectively.

[0086] Upper electrode Pt [0.25 μm]/Ti [0.05 μm]//piezo-electrostrictivefilm PZT (001) [3 μm]//lower electrode La-STO (100) [0.05 μm]//vibrationplate YSZ (100) [2 μm]/substrate Si (100) [600 μm] TABLE 1 La-STO La-STOPZT La doping Lattice orientation PZT concentration constant ratioCrystalline (%) (A) (001) (%) system Embodiment 1 0.08 3.923 93tetragonal Embodiment 2 0.80 3.941 94 tetragonal Embodiment 3 8.00 4.02199 tetragonal Embodiment 4 0.04 3.911 89 tetragonal

[0087] From the relations of the changes in the La doping concentrationin SrTiO₃ and the lattice constants of the La-STO shown in the Table 1,it is understood that with the increases in the La doping concentration,the lattice constant of La-STO becomes larger. Further from therelations of the changes in the La doping concentration and the PZTorientation ratio, it is understood that with the increases in the Ladoping concentration, the orientation ratio becomes larger. Also, whenthe La doping concentration is 0.04%, which is less than 0.05%, theorientation ratio is 89%, which is less than 90%. Also, the crystallinesystems are all tetragonal.

[0088] In Table 2, the displacement amounts are shown at the time ofapplying 20 V to each of the actuators. For this Table, it isunderstandable that the displace amount of the first embodiment havingthe La doping concentration of 0.08% is 278 nm. Likewise, that of thesecond embodiment of 80% is 469 nm. That of the third embodiment of 8.0%is 378 nm. Also, the displacement amount of the fourth embodiment havingthe La doping concentration of 0.04%, which is less than 0.05% is 42 nmby the application of 20 V. There is a need for the application of 60 Vthereto in order to obtain substantially the same displacement amount ofthe first to third embodiments. When 60 V is applied, the displacementamount thereof is 312 nm. TABLE 2 Displacement amount (nm) Embodiment 1278 Embodiment 2 469 Embodiment 3 378 Embodiment 4  42 Embodiment 4 312(60 V (10 kHz) applied)

Fifth to Eighth Embodiments

[0089] Using the actuators of the first, second, third, and fourthembodiments liquid discharge heads each having the structure as shown inFIG. 3 are manufactured, and adopted as the fifth, sixth, seventh, andeight embodiments, respectively.

[0090] The film thickness of each film is arranged as described earlier,and the upper electrode is 0.3 μm/the piezo-electrostrictive film, 3μm/the lower electrode, 0.5 μm/the vibration plate, 2 μm/the substrate600 μm. Also, in order to implement the 180 dpi, the width of thepressure chamber is arranged to be 90 μm, and the width of pressurechamber wall is 50 μm.

[0091] The Table 3 shows the discharge amount of liquid droplet anddischarge speed of each of the liquid discharge heads at the time ofapplying 20 V at 10 kHz. TABLE 3 Discharge amount Discharge speed (p1)(m/sec) Embodiment 5 12 12 Embodiment 6 17 14 Embodiment 7 15 13Embodiment 8  8  8 Embodiment 8 12 (60 V (10 kHz) applied) 12 (60 V (10kHz) applied)

[0092] With the liquid discharge heads of the fifth to seventhembodiments, it is possible to obtain the discharge amounts of 12 to 17pl, and the discharge speeds of 12 to 14 m/sec, respectively.

[0093] Also, when 20 V is applied to the liquid discharge head of theeighth embodiment having the actuator, the La doping concentration ofthe lower electrode of which is 0.04%, that is, less than 0.05%, thedischarge amount is 8 pl, and the discharge speed is 8 m/sec. Thesevalues are smaller than the discharge amounts and discharge speedsobtainable by the fifth to seventh embodiments. There is a need for theapplication of 60 V for the liquid discharge head of the eighthembodiment in order to obtain substantially the same discharge amountand discharge speed as those of the fifth to seventh embodiments. When60 V is applied, the discharge amount thereof is 12 pl, and thedischarge speed, 12 m/sec.

What is claimed is:
 1. An actuator comprising: a laminated structurehaving a vibration plate, a lower electrode, a piezoelectric element,and an upper electrode laminated sequentially on a basic element,wherein at least said lower electrode of said two electrodes is a thinoxide film of La-doped single orientated crystal or monocrystalcontaining Sr and Ti.
 2. An actuator according to claim 1, wherein thepiezoelectric element is a thin oxide piezo-electrostrictive film ofsingle orientated crystal or monocrystal.
 3. An actuator according toclaim 1, wherein the La doping concentration in the electrode of thinoxide film of single orientated crystal or monocrystal is within a rangeof 0.05 atm % to 10 atm %
 4. An actuator according to claim 1, whereinthe lattice constant of the electrode of thin oxide film of singleorientated crystal or monocrystal is within a range of 3.905 Å to 4.030Å
 5. An actuator according to claim 1, wherein the film thickness of theelectrode of thin oxide film of single orientated crystal or monocrystalis within a range of 50 nm to 5,000 nm.
 6. An actuator according toclaim 1, wherein the crystal orientation of the electrode of thin oxidefilm of single orientated crystal or monocrystal is either one of (010),(101), (110), and (111).
 7. An actuator according to claim 1, whereinthe crystal orientation ratio of the electrode of thin oxide film ofsingle orientated crystal or monocrystal is 95% or more.
 8. An actuatoraccording to claim 1, wherein the piezoelectric element is a thin oxidepiezo-electrostrictive film of single orientated crystal or monocrystalcontaining Pb, and at least either one of Zr, Ti, Ni, Nb, Mg, Zn, andSc.
 9. An actuator according to claim 8, wherein the crystal orientationratio of the thin oxide piezo-electrostrictive film of single orientatedcrystal or monocrystal is 90% or more.
 10. An actuator according toclaim 8, wherein the crystalline system of the thin oxidepiezo-electrostrictive film of single orientated crystal or monocrystalis rhombohedral or tetragonal.
 11. An actuator according to claim 8,wherein the film thickness of the thin oxide piezo-electrostrictive filmof single orientated crystal or monocrystal is 500 nm or more and 10 μmor less.
 12. A liquid discharge head provided with a main body portionhaving the actuator according to claim 1, and pressure chamber formedwith opening portion on a part thereof, and communicated with liquiddischarge port, wherein said actuator is provided on said pressurechamber so as to close said opening portion.
 13. A liquid discharge headprovided with a main body portion having the pressure chambercommunicated with liquid discharge port, and an actuator provided onsaid main body portion corresponding to said pressure chamber, whereinsaid actuator comprises a laminated structure having a vibration plate,a lower electrode, a piezoelectric element, and an upper electrodelaminated sequentially on said main body portion, and at least saidlower electrode of said two electrodes is a thin oxide film doped withLa of single orientated crystal or monocrystal containing Sr and Ti. 14.A method for manufacturing a liquid discharge head provided with themain body portion having pressure chamber communicated with liquiddischarge port, and an actuator provided on said main body portioncorresponding to said pressure chamber, comprising the following stepsof: filming a vibration plate on said main body portion; filming on saidvibration plate a lower electrode of thin oxide film of singleorientated crystal or monocrystal containing La doped Sr and Ti; filmingon said lower electrode a perovskite type thin oxidepiezo-electrostrictive film filming an upper electrode on saidperovskite type thin oxide piezo-electrostrictive film; and forming saidpressure chamber.